title: Identification and characterization of the second cysteine protease inhibitor of Clonorchis sinensis (CsStefin-2).
abstract: CsStefin-2, the second cysteine protease inhibitor of Clonorchis sinensis, was identified and characterized. CsStefin-2 is a cysteine protease inhibitor that belongs to family 1 stefins based on its phylogenetic and structural properties. However, CsStefin-2 had a QIVSG cystatin motif distinct from the common QVVAG cystatin motif that is well conserved in family 1 stefins. Mutagenesis analysis revealed that the two amino acid substitutions in the QIVSG cystatin motif of CsStefin-2 did not affect its inhibitory activity. Molecular modeling also indicated that no critical change was induced in the interaction between CsStefin-2 and its target enzyme. CsStefin-2 showed broad inhibitory activities against several cysteine proteases, including human cathepsins B and L, papain, and cathepsin Fs of C. sinensis (CsCFs), and effectively inhibited the autocatalytic maturation of CsCF-6. Native CsStefin-2 was assembled into a homo-tetramer, in which intermolecular disulfide bonds are not involved in the assembly of the tetramer. CsStefin-2 was expressed throughout the various developmental stages of the parasite and was localized in the intestinal epithelium, where CsCFs are actively synthesized. These results suggest that CsStefin-2 is the second active cysteine protease inhibitor of C. sinensis that shares functional redundancy with CsStefin-1 to modulate the activity and processing of CsCFs.
authors.affiliation: Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju, 660-751, Republic of Korea.
authors.forename: Jung-Mi
authors.initials: JM
authors.lastname: Kang
authors.forename: Hye-Lim
authors.initials: HL
authors.lastname: Ju
authors.forename: Kon Ho
authors.initials: KH
authors.lastname: Lee
authors.forename: Tong-Soo
authors.initials: TS
authors.lastname: Kim
authors.forename: Jhang Ho
authors.initials: JH
authors.lastname: Pak
authors.forename: Woon-Mok
authors.initials: WM
authors.lastname: Sohn
authors.forename: Byoung-Kuk
authors.initials: BK
authors.lastname: Na
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002401:Cathepsin B / Q000037:antagonists & inhibitors; D056668:Cathepsin L / Q000037:antagonists & inhibitors; D003001:Cloning, Molecular; D003004:Clonorchis sinensis / Q000235:genetics* / Q000378:metabolism; D015891:Cystatins / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000235:genetics / Q000378:metabolism*; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010206:Papain / Q000037:antagonists & inhibitors; D010802:Phylogeny; D017434:Protein Structure, Tertiary
chemical_list: D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D015801:Helminth Proteins; D002401:Cathepsin B; D056668:Cathepsin L; D010206:Papain